Fix an issue "Cannot obtain key {!r} from key-value storage" in scheduler

Scheduler may fail with the following log on the full launch:

2023-06-24 21:30:09,967 (__init__.py:393) root ERROR> An error occurred:
Traceback (most recent call last):
  File "/home/oseuser/klever/klever/scheduler/schedulers/__init__.py", line 287, in launch
    elif desc["status"] == "PROCESSING" and self.runner.process_task_result(task_id, desc)
  File "/home/oseuser/klever/klever/scheduler/schedulers/runners.py", line 470, in process_task_result
    solution = utils.kv_get_solution(self.logger, self.scheduler_type(), identifier)
  File "/home/oseuser/klever/klever/scheduler/utils/__init__.py", line 626, in kv_get_solution
    raise RuntimeError("Cannot obtain key {!r} from key-value storage".format(key))
RuntimeError: Cannot obtain key 'solutions/Klever/31217' from key-value storage
2023-06-24 21:30:30,542 (runners.py:329) root ERROR> Job b2b04a06-7d44-4848-98ef-7810c977f6e7 has failed: SchedulerException('Exited with exit code: 255 (please, inspect unknown reports and logs)')
2023-06-24 21:30:30,544 (runners.py:368) root ERROR> Cannot process results of task 31217: SchedulerException('Exited with exit code: 1 (please, inspect unknown reports and logs)')